Synthetic auxin herbicides are widely used because of their effective control of broadleaf weeds and safety in many turfgrass species. However, two synthetic auxin herbicides, triclopyr and aminocyclopyrachlor (AMCP; DPX-KJM44), are known to injure warm-season turfgrasses. Our objective was to quantify this injury through evaluations of turfgrass quality and turfgrass green cover in response to herbicide treatment. The results of this study indicate that relative to the labeled use rates of triclopyr (0.56 to 1.12 kg ae ha−1) and AMCP (0.053 kg ai ha−1), zoysiagrass is the only turfgrass tested with sufficient tolerance to the respective compounds for their use as weed-control agents. Bermudagrass and centipedegrass may be injured by triclopyr and AMCP at labeled rates, characterized by a reduction in turfgrass quality and green cover. St. Augustinegrass is not tolerant of either triclopyr or AMCP at labeled rates.
Nomenclature: Aminocyclopyrachlor-methyl, DPX-KJM44; triclopyr; centipedegrass, Eremochloa ophiuroides (Munro) Hack.; hybrid bermudagrass, Cynodon dactylon (L.) Pers. × Cynodon transvaalensis Burtt Davy ‘Tifsport’; hybrid zoysiagrass, Zoysia japonica Steud.‘Emerald’; St. Augustinegrass, Stenotaphrum secundatum (Walt.) Kuntze ‘Palmetto’; zoysiagrass, Zoysia japonica Steud. ‘Meyer’ and ‘Zenith’.